As examples of the prior art, reference is made in particular to GB Patent No. 1278501, DE Patent No. 3822877, U.S. Pat. No. 4,759,561 and a chair marketed under the trademark STRESSLESS. The last mentioned chair type is characterised by, among others, the feature that the body's centre of gravity relative to the chair is maintained almost constant, usually close to or over the central column of the chair, if the chair is of the swivelling type. However, an important point with the known type of chair is that when the backrest is tilted backwards, the lower end of the chair back remains at the same level as the back edge of the chair seat. This is because the seat back and the chair seat are connected to each other at the lower edge of the chair back and the back edge of the chair seat respectively. When the chair user leans backwards in the chair, he may experience the sensation of the chair back apparently “climbing” a little up his back. When the user leans backwards, it is of course important that the neck rest and the like are felt to be approximately in the same place regardless of the sitting position.
This problem area is no less important in connection with adjustable wheelchairs, where it is usual to be able to adjust the back rest relative to a fixed seat or to allow the seat and the back to be rigidly connected to each other and to be tiltable or adjustable as one unit. Furthermore, it has been known in connection with adjustable wheelchairs that they require at least one stabiliser that projects backwards from the large wheelchair wheels in order to prevent the chair from tipping backwards when the chair user leans back in the chair.
In the aforementioned prior art chairs, a change of sitting position results in a major change of the body's centre of gravity.
Reference will also be made to NO 300754 wherein the chair back at a first point of support on each side thereof is pivotally connected to a respective side member of the chair and at a second point of support forms an articulated connection with a rear portion of the chair seat frame, and wherein the chair seat frame at a forward point of support on each side thereof is slidably connected to respective side members along a front, forward and upward sloping guide that is an integral part of the side member. The first point of support on the chair back is arranged to slide along a rear, forward and downward sloping guide in the side member, and the seat frame has on each side a rear point of support between the front point of support point and the second point of support for the chair back, the rear point of support forming a sliding connection with a guide in the respective side member, and central when seen in the longitudinal direction of the side member, and which is either horizontal or slightly forward and upward sloping. With this solution, a relatively limited change of the body's centre of gravity is obtained. Nevertheless, there are still deficiencies in this art which mean that there continues to be a great need for improvements in the field.
Accordingly, it has been an object of the present invention to provide an adjustable chair of the aforementioned type, wherein the aforementioned deficiencies both in ordinary adjustable chairs of this kind and especially in wheelchairs can be remedied. The primary object of the invention is to provide good sitting comfort in an adjustable chair of this kind, and when the invention is used in connection with a manual wheelchair, the otherwise good sitting comfort of the comfort wheelchair could be combined with the wheeling and transport properties of the active wheelchair. A particular object of the present invention in connection with a wheelchair is to combine an “active driving position” and a “passive resting position” in one and the same wheelchair.